Heparan Sulfate-related Oligosaccharides in Ternary Complex Formation with Fibroblast Growth Factors 1 and 2 and Their Receptors

Nadja Jastrebova,Maarten Vanwildemeersch,Alan C Rapraeger,Guillermo Giménez-Gallego,Ulf Lindahl,Dorothe Spillmann

doi:10.1074/jbc.m600806200

Abstract

Biosynthesis of heparan sulfate (HS) is strictly regulated to yield products with cell/tissue-specific composition. Interactions between HS and a variety of proteins, including growth factors and morphogens, are essential for embryonic development and for homeostasis in the adult. Fibroblast growth factors (FGFs) and their various receptors (FRs) form ternary complexes with HS, as required for receptor signaling. Libraries of HS-related, radiolabeled oligosaccharides were generated by chemo-enzymatic modification of heparin and tested for affinity to immobilized FR ectodomains in the presence of FGF1 or FGF2. Experiments were designed to enable assessment of N-sulfated 8- and 10-mers with defined numbers of iduronic acid 2-O-sulfate and glucosamine 6-O-sulfate groups. FGF1 and FGF2 were found to require similar oligosaccharides in complex formation with FR1c-3c, FGF2 affording somewhat more efficient oligosaccharide recruitment than FGF1. FR4, contrary to FR1c-3c, bound oligosaccharides at physiological ionic conditions even in the absence of FGFs, and this interaction was further promoted by FGF1 but not by FGF2. In all systems studied, the stability of FGF-oligosaccharide-FR complexes correlated with the overall level of saccharide O-sulfation rather than on the precise distribution of sulfate groups.

Highlights

Heparan sulfate (HS)2 proteoglycans are abundant on cell surfaces and in the extracellular matrix
The results point to non-selective involvement of oligosaccharides in complexes between both growth factors and FR1c, FR2c, and FR3c, whereas FGF1 and FGF2 differ in their saccharide requirement for complex formation with FR4
Formation of fibroblast growth factors (FGFs)-Heparin-FGF receptors (FRs) Ternary Complex—The ability of HS-related oligosaccharides to support formation of ternary complexes with FGFs and FRs was assessed by affinity chromatography of radiolabeled oligosaccharides on immobilized FR1⁄7AP in the presence of the growth factors

Summary

Introduction

Heparan sulfate (HS)2 proteoglycans are abundant on cell surfaces and in the extracellular matrix. Complex formation, large [3H]heparin oligomers (Ͼ18-mers) (Fig. 1A) were applied to the receptor columns in the presence or absence of FGFs. In the absence of FGF, the oligosaccharides emerged quantitatively in the unbound pool (unretarded in 0.15 M NaCl) from each of the receptors FR2c (Fig. 1B), FR1c, or FR3c (data not shown).

Results

Conclusion